Gas turbines operate under extreme conditions. In order to drive efficiency higher, there have been continual developments to allow operation of gas turbines at ever higher temperatures. As the temperature of the hot gas path increases, the temperature of adjacent regions of the gas turbine necessarily increase in temperatures, due to thermal conduction from the hot gas path.
In order to allow higher temperature operation, some gas turbine components, such as nozzles and shrouds, have been divided such that the higher temperature regions (the fairings of the nozzles and the inner shrouds of the shrouds) may be formed from materials, such as ceramic matrix composites, which are especially suited to operation at extreme temperatures, whereas the lower temperature regions (the outside and inside walls of the nozzles and the outer shrouds of the shrouds) are made from other materials which are less suited for operation at the higher temperatures, but which may be more economical to produce and service.
Joining the portions of gas turbines in higher temperature regions to the portions of gas turbines in lower temperature regions may present challenges, particularly with regard to interfaces which include seals. Seals will contact both the higher temperature portions and the low temperature portions, and therefore are subjected to heat conduction from the hotter portion of the turbine to the cooler portion of the turbine. Certain types of seals which have beneficial properties, such as elastic or spring-like seals, may be unsuitable for operation in contact with the higher temperature portions, as these seals may creep at the elevated temperatures, resulting in degradation of operational characteristics.